Although it has never happened to me..I have heard some people say that in the morning there is like a slick of 'oil' on top of the toilet bowel water...just very thin like an oil slick.
I would think this is a sign that the bile isn't being released properly to digest the oil. Or that the walls of your intestines are caked with too much mucoid plaque, to let the good parts of the oil absorb into you. Possibly?